The thrombin clottable moieties of plasma, which contain fibrinogen/fibrin antigenic determinants, are commonly referred to as plasma "fibrinogen." However, plasma "fibrinogen," because of the presence of high molecular weight fibrinogen/fibrin complexes, native fibrinogen and derivatives of fibrinogen smaller than the native molecule, is biochemically and biophysically inhomogeneous. These individual moieties, differing in molecular weight, may be qualified in plasma by gel exclusion chromatography. Substantial evidence supports the view that the proportions and concentrations of high molecular weight fibrinogen/fibrin complexes (HMWFC) reflect the rate of fibrin formation in vivo and that the finding of "pathological" increase in plasma HMWFC (values exceeding mean plus 2 s.d. of normal) is correlated with the presence of identifiable thromboembolic vascular disease, a thrombus or intravascular coagulation. We propose (a) to construct a fully-automated apparatus for performing plasma fibrinogen chromatography, (b) investigate the biochemical composition of plasma HMWFC with a main aim of developing methods for distinguishing between fibrinogen and fibrin-derived moieties, (c) to compare, in a collaborative study with other investigators, plasma fibrinogen chromatographic findings with other methodologies (e.g., fibrinopeptide A, etc.), designed to detect intravascular coagulation in patients with acute thromboembolic vascular disease, (d) extend our studies on the use of plasma fibrinogen chromatography as an aid to the control of antithrombotic therapy, (e) determine whether the presence of documented atherosclerosis alters plasma HMWFC concentration and other blood coagulation findings and (f) whether administration of clofibrate to hyperlipidemia type II and type IV patients is associated with plasma HMWFC reduction.